The present invention relates generally to capacitive fingerprint sensors, and more particularly to improvements in the structure of sensing elements that capacitively interact with the fingerprint-bearing skin of a user's finger.
A capacitive distance sensor is disclosed in commonly-assigned U.S. Pat. No. 6,114,862 by Tartagni et al., the disclosure of which is hereby incorporated by reference. The Tartagni et al. patent discloses the basic structure and operation of a conventional solid-state fingerprint sensor that is formed on a single semiconductor chip. FIGS. 1 and 2 herein correspond to FIGS. 1 and 4 of the Tartagni et al. patent, and are briefly described below to facilitate an understanding of the application of the present invention in the context of a two-dimensional fingerprint sensor array.
The present invention provides an improvement in the capacitive sensing element that is replicated in each of the sensor cells or “pixels” that are included in a two-dimensional array of sensor cells. Several embodiments of the improved sensing element are described.